1. Field of the Invention
The present invention relates to an improved filtration and washing apparatus which includes a tapered rotary cylinder and a rotary filtration cylinder disposed around the tapered rotary cylinder. More particularly, the present invention relates to an improved filtration and washing apparatus having a control valve means which is actuated for controlling the pressure in a treatment zone between a tapered rotary cylinder and a rotary filtration cylinder.
2. Prior Art of the Invention
Many types of apparatus for filtrating and washing waste product are known in the art. It is common practice in the prior art to use vacuum filter apparatuses, centrifugal separators, or roller presses, etc. However, since the dehydrated filth contains a high degree of water, there arises the problems of fuel expense for drying and burning up the filth as well as the transportation charges.
According to the U.S. Pat. Nos. 4,615,801 entitled "rotary filtration means in the filth condensation-dehydration apparatus" and 4,755,291 entitled "filtration and washing apparatus with adjustable rotary filtration cylinder" owned by the inventor of the present invention, filtration apparatuses are disclosed which include a control valve associated with an outlet thereof. However, since the control valve is operated by hand, it is very difficult to accurately control the pressure in the treatment zone. Furthermore, since the control valve is moved by fastening or loosening a pair of bolts, the disc-type control valve cannot uniformly fasten or loosen an outlet aperture disposed in the rear end of the treatment zone.